1. Field of the Invention
The invention generally relates to rotors for heavier than air craft, and more particularly to an improved rotor blade capable of simultaneously utilizing components of lift and centrifugal forces for establishing a desired pitch angle for the blade.
2. Description of the Prior Art
Rotors for helicopters and the like are often equipped with pitch control mechanisms which serve to dictate the instantaneous pitch angle for the rotor blades, for thus establishing a desired coefficient of lift.
One technique for achieving pitch control is embodied in the concept of providing each rotor blade with a flap or aileron located at its trailing edge, the angular position of which may be cyclically adjusted for varying the pitch of the blade. Such a system is described in U.S. Pat. No. 2,443,393.
Another system heretofore suggested for use in achieving pitch control includes a pair of fly-ball weights upon which centrifugal force is exerted for actuating pitch control linkages which vary the pitch angles for the blades. Such a system is disclosed in U.S. Pat. No. 2,614,637.
Systems referred to as the Girvaions-Dorand system which includes pressure sensing devices, for sensing changes in pressure on rotor blades, connected with signal processing circuits which serve to transmit error signals to trailing edge flaps, also have been suggested for initiating changes in effective pitch angles for rotor blades.
Finally, it has been suggested that pivotal trailing edge flaps controlled by cam-actuated linkages, responsive to centrifugal forces, can be employed in controlling the pitch angles for rotor blades. For example, such is disclosed in U.S. Pat. No. 3,215,370.
Unfortunately, generally speaking, while the systems previously mentioned function satisfactorily for their intended purposes, it should be appreciated that each of the systems of the prior art fails to totally satisfy existing needs. For example, where fly-balls are used in controlling the pitch of a pitchable blade, weight and complexity factors tend to impair performance, where pressure sensors are employed complexity is increased, and, in any event, where trailing edge flaps are provided for a blade, maximum lift capabilities are sacrificed in establishing the negative flap deflection required for increasing the angle of attack for the blade.
Accordingly, it can be appreciated that among the disadvantages of the systems of the prior art are those which may be classified generally as follows: complexity in structure; reduction in lift capability; excessive costs in terms of economics; redundancy; and lack of reliability.
It is therefore the general purpose of the instant invention to provide a simplified, economic, highly reliable, variable pitch rotor blade for use in rotors for heavier than air craft which overcomes the aforementioned disadvantages and inadequacies of rotor blades previously suggested and employed.